1. Field of the Invention
This invention pertains to the field of electronic imaging and, more particularly, to an image acquisition peripheral operated as an input device to a personal computer or professional workstation.
2. Background Art
Video cameras and computer frame grabbers are well known in the prior art. A typical system employs a video motion camera (such as the CCD 4000 RGB Flash-Sync Camera manufactured by Eastman Kodak Co., Rochester, N.Y.) and a frame grabber board (such as a TARGA.TM. frame store board manufactured by True Vision, Inc., Indianapolis, Ind.) attached to the PC bus of a personal computer or professional workstation. The camera provides the timing to interface with the video frame store board by activating the frame acquire line of the frame store board whenever an external voltage input to the camera is dropped low (e.g., by dropping the "Camera Acquire In" line to the CCD 4000 camera). While the external voltage input may be separately and directly enabled, it is customary when using a video camera (such as the CCD 4000 camera) with a personal computer to design software to activate the camera's frame acquire line from the computer. To capture an image into the computer in such a customary application, the operator frames the subject while observing the live camera output on a video monitor, and then interacts with the computer keyboard at the proper moment. The need to use the computer keyboard frequently interferes with effective use of the camera.
Other known scanners that interact with a host computer include U.S. Pat. No. 4,901,364 (Faulkerson et al) and U.S. Pat. No. 4,581,761 (Ichinokawa et al). Faulkerson et al describes an interactive linear scanner system (for text) in which a hand-operated optical scanner includes a plurality of function keys that are user-programmable so as to assume certain functions that are ordinarily accessed through a keyboard. For instance, the function keys can be programmed to provide movement from field-to-field within a spreadsheet program while entering data using the scanner, without, e.g., requiring the user to use arrow keys on the computer keyboard. The camera exposure functions, however, such as control of a light source and the enablement of the optical scanning function, are controlled by a video processor located in the scanner. Moreover, the image data is edited to eliminate duplicative character information between successive image data frames. The edited frame data is then transmitted via data bus to a host computer. In Ichinokawa et al, a video processor is detached from a hand-operated scanner. A switch on the bottom of the scanner triggers the detached processor when the scanner is pushed down upon a document. The processor then receives image data and additional information (e.g., for switching from draw to erase, setting coordinates, and changing magnification) from the scanner, in turn providing processed data to a host computer.
As alluded to earlier, it is desirable to disassociate the camera from keyboard interaction to the extent possible. In one desirable application, a low cost electronic still camera would be tethered to a small, battery operated notebook or penpad personal computer which provides image processing, storage, and display of the captured images. By relying on the computer to perform these tasks, the camera cost can be greatly reduced. In such an application, the computer would typically be slung over the shoulder or rested on a table, while the user held the camera to compose the image. However, if the user must press buttons or pointers on the computer to capture each image, as is typical in the prior art, the system will be very unwieldy to use since the user will have to hold the camera in the right position with one hand, while operating the computer with the other hand.
By tethering the camera to the computer, as exemplified by the Faulkerson et al patent, it is possible to have both complex camera exposure functions and to control some computer functions from the camera itself. The complex camera exposure functions remain in the camera, however, which is contrary to the objective of low cost. Though it may be feasible, as done in the prior art, to download most complex processing to the computer, in effect slaving the camera to the computer, it is desirable to maintain the ergonomics of a hand-held camera, that is, to permit framing, exposure, flash, status indication, etc., without having to interact with the host computer. What is needed is a design for a tethered computer camera and associated computer software that allows the user to easily capture and store multiple images from the camera into the computer disk memory, without needing to interact with the computer at the instant each image is captured.